With progress of technology of fabricating high-integration semiconductor devices in recent years, circuit wiring patterns or interconnections have been becoming increasingly small and fine, and spacings between wiring patterns have also been decreasing. As these wiring spacing decreases, a depth of focus becomes shallower in circuit pattern formation by performing photolithography or the like. In a case of photolithography for less than 0.5-μm designs in particular, surfaces of semiconductor wafers on which circuit pattern images are to be formed by a photolithographic apparatus require a higher degree of surface flatness because of a photolithography depth of focus. To realize a required degree of surface flatness, polishing using a polishing apparatus is widely adopted.
A polishing apparatus of this type has a turntable with a polishing cloth bonded to a top thereof to form a polishing surface. The polishing apparatus further has a top ring as a substrate holding mechanism. The turntable and the top ring rotate independently of each other at respective numbers of revolutions. A substrate to be polished that is held by the top ring is pressed against a polishing surface of the turntable while a polishing solution is being supplied onto the polishing surface, thereby polishing a surface of the substrate to a flat and specular surface. After completion of polishing, the substrate is released from the top ring body and transferred to a subsequent process, e.g. a cleaning process.
In the above-described polishing apparatus, a substrate holding part of the top ring, which holds the substrate to be polished, may be deformed by frictional heat generated during polishing of the substrate. Further, a polishing capability may vary owing to a temperature distribution on the polishing surface. Such deformation of the substrate holding part of the top ring and variations of the polishing capability cause a substrate polishing function to be degraded. Further, this type of polishing apparatus polishes the substrate while supplying a polishing solution, e.g. a slurry, onto the polishing surface of the polishing table, as stated above. The polishing solution is likely to adhere to an outer surface of the top ring, particularly an outer peripheral surface thereof, and to dry thereon. If dried solid matter drops onto the polishing surface, an adverse influence is exerted on a polishing process.
To prevent deformation of the substrate holding part of the top ring due to frictional heat generated during polishing of the substrate, JP-A-11-347936 (Japanese Patent Application Unexamined Publication) discloses that a material of good thermal conductivity is attached to a substrate holding part (wafer holder) to make a temperature distribution uniform, and a refrigerant flow passage is provided in the substrate holding part to supply a refrigerant through the refrigerant flow passage to cool the substrate holding part, and further, fins are provided on the substrate holding part to promote heat dissipation. However, the method disclosed in JP-A-11-347936 is still insufficient to effectively cool an outer peripheral portion (particularly a guide ring) of the substrate holding part of the top ring, and hence suffers from a problem in that a polishing solution, e.g. a slurry, may adhere to the outer peripheral portion of the substrate holding part and dry to stick fast thereto, together with polishing dust generated from the substrate by polishing.
With an increase in diameter of semiconductor substrates, an area of contact between a polishing pad on the polishing table and the substrate to be polished has increased. Consequently, a temperature tends to rise during polishing the substrate. Meanwhile, it has become common practice to use substrate polishing apparatus having a complicated mechanism for a purpose of controlling a polishing profile. Many of the polishing apparatus employ a method whereby a component part having a high coefficient of friction is pressed into contact with a polishing pad in the complicated mechanism. This may also cause a rise in temperature during polishing.
The rise in temperature during polishing of the substrate exerts an influence on a surface of the polishing pad and slurry components, and causes degradation of flatness of a polished surface of the substrate obtained with the polishing apparatus and a polishing rate, and also makes it impossible to maintain a desired flatness and polishing rate stably.